1. Field of the Invention
The present invention relates to a durable thermal transfer image. Specifically, it relates to a subsurface imaged thermal transfer label and a method of manufacture.
2. Brief Description of Related Art
Thermal transfer printing traditionally involves variably boding ink from a thin PET carrier (ink, carrier, and release coating comprising a ribbon) to a substrate. A positive image is printed on a substrate. The PET carrier is then stripped away from the substrate, removing the ink from all areas that have not been bonded via heat and pressure. While the printed image is fairly durable, it is subject to attack from abrasion and chemicals, particularly solvents similar to the ones used to coat the ink on the PET carrier.
Traditional approaches to improving durability of the image have required a separate process to overlaminate the printed image with a protective film (usually coated with a pressure sensitive adhesive). This adds complexity to the process, and typically requires either costly equipment or manual labor. Extensive development work has been undertaken to improve the durability of the thermal transfer inks, but some chemicals (usually solvents such as MEK, xylene, toluene, etc.) are still extremely damaging to the printed image.
Chemical resistance is a common challenge in industrial labeling applications, laboratory tracking applications, and other markets. Existing solutions involve costly and unwieldy overlaminating/diecutting stations, extensive manual labor, or expensive and marginally effective ribbon ink. Durable thermal transfer printing applications typically require an expensive, resin based ribbon to achieve good levels of durability.
Many customers are unwilling to overlaminate their labels by hand by applying a separate clear label, and are not interested in the additional cost of the overlaminate film.